/Engine/Source/Runtime/Engine/Public/MaterialCompiler.h
Pushes a node of the Strata tree being walked. A node is caracterised by an expression and its input path taken.
[FGuid](API\Runtime\Core\Misc\FGuid) StrataTreeStackPush ( [UMaterialExpression](API\Runtime\Engine\Materials\UMaterialExpression) * Expression, uint32 InputIndex )